what should I do if I want to make this?

[Wang Yige]

Hi everyone,

I am a beginner of Flex and Bison and just know litter about them ,I need 
your help.

I want to encapsulate a C++ class ,which can works like a calculator,its 
structure seems like this:
Class Calc
{
public:
 calc(){};
 ~calc(){};

 void setExpr(char *cExpr){this.cExpr = cExpr;}
 char* getExpr(){ return this.cExpr;}

 double getResult(){return result;}

 void lexParse(){ yylex(this.cExpr);...}

 //in yylex, result will be evaluated...
 ....

private:
 char *cExpr;
 double result;
 
};

If somebody wants to use my Calc, he just use it like this:

Calc calcer;
calcer.setExpr("1+2*3");//the expression to calculate 
calcer.lexParse();
double dRet = calc.getResult();//the result of the expression 

As you know ,my calculator's core function in lexParse(), in which I want 
to use Flex & Bison, I have install Bison2.3 on my HP-Unix OS and I have 
view the bison manual and its example of calc++,but I find it is not as 
easy as my calculator in use.

There are more wonders on my calculator' structure than its functions(I 
just take it as an example ,even though it can only calculate "1+1").

In a word, Can yylex ,yyparse() be encapsulated into a C++ Class ?

Anybody 's any help is appreciated very much!

Thanks for Hans Aberg's help has offered to me!

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